Effects of microRNA-24 targeting C-myc on apoptosis, proliferation, and cytokine expressions in chondrocytes of rats with osteoarthritis via MAPK signaling pathway

VEGFA, MYC, and JUN are abnormally elevated in the synovial tissue of patients with advanced osteoarthritis

Osteoarthritis (OA), affecting > 500 million people worldwide, profoundly affects the quality of life and ability to work. The mitogen-activated protein kinase (MAPK) signaling pathway plays an essential role in OA. To address the lack of studies focused on synovial cells in OA, we evaluated the expression patterns and roles of the MAPK signaling pathway components in OA synovial tissues using bioinformatics. The JUN, MYC, and VEGFA expression levels were significantly higher in the synovial tissues of patients with OA than in control tissues. These loci were closely related to abnormal proliferation, inflammation, and angiogenesis in the synovial tissues of patients with OA. We speculate that Myc and VEGFA activate the p38-MAPK signaling pathway to further activate Jun, thereby promoting abnormal inflammation, proliferation, and angiogenesis in OA synovial tissue. The high MYC, JUN, and VEGFA expression was positively correlated with the patients' K-L score, pain time, and synovial score. Furthermore, the high p38-MAPK and P-p38-MAPK expression confirmed that the abnormal expression and activation of the MAPK signaling pathway occurred in the synovial tissue of patients with OA. Our findings may provide a new direction for the clinical diagnosis and treatment of OA and insights into its pathogenesis.

Regulation of ferroptosis in osteoarthritis and osteoarthritic chondrocytes by typical MicroRNAs in chondrocytes

Osteoarthritis (OA) is a progressive degenerative disorder impacting bones and joints, worsened by chronic inflammation, immune dysregulation, mechanical stress, metabolic disturbances, and various other contributing factors. The complex interplay of cartilage damage, loss, and impaired repair mechanisms remains a critical and formidable aspect of OA pathogenesis. At the genetic level, multiple genes have been implicated in the modulation of chondrocyte metabolism, displaying both promotive and inhibitory roles. Recent research has increasingly focused on the influence of non-coding RNAs in the regulation of distinct cell types within bone tissue in OA. In particular, an expanding body of evidence highlights the regulatory roles of microRNAs in OA chondrocytes. This review aims to consolidate the most relevant microRNAs associated with OA chondrocytes, as identified in recent studies, and to elucidate their involvement in chondrocyte metabolic processes and ferroptosis. Furthermore, this study explores the complex regulatory interactions between long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) in OA, with an emphasis on microRNA-mediated mechanisms. Finally, critical gaps in the current research are identified, offering strategic insights to advance the understanding of OA pathophysiology and guide therapeutic developments in this field.

MiR-19b-3p Attenuates Chondrocytes Injury by Inhibiting MAPK/NF-Κb Axis via Targeting SOCS1

In this study, miR-19b-3p was downregulated in osteoarthritic cartilage tissues and IL-1β-stimulated primary chondrocytes, and miR-19b-3p overexpression reversed the inhibitory effect of IL-1β on cell viability, the promotion effects of apoptosis, inflammatory factor secretion and extracellular matrix degradation, whereas the opposite effect was observed with miR-19b-3p inhibitor. Moreover, SOCS1 is a target gene of miR-19b-3p. Furthermore, SOCS1 overexpression enhanced cell injury compared with IL-1β alone treatment, whereas knockdown of SOCS1 restored cell damage caused by IL-1β. Further studies revealed that miR-19b-3p promoted chondrocyte injury repair by suppressing SOCS1 expression, and we found that was mediated by blocking the MAPK/NF-κB axis. Taken together, our findings may provide a new therapeutic strategy for osteoarthritis.

The Added Value of the “Co” in Co-Culture Systems in Research on Osteoarthritis Pathology and Treatment Development

Osteoarthritis (OA) is a highly prevalent disease and a major health burden. Its development and progression are influenced by factors such as age, obesity or joint overuse. As a whole organ disease OA affects not only cartilage, bone and synovium but also ligaments, fatty or nervous tissue surrounding the joint. These joint tissues interact with each other and understanding this interaction is important in developing novel treatments. To incorporate and study these interactions in OA research, several co-culture models have evolved. They combine two or more cell types or tissues and investigate the influence of amongst others inflammatory or degenerative stimuli seen in OA. This review focuses on co-cultures and the differential processes occurring in a given tissue or cell as a consequence of being combined with another joint cell type or tissue, and/or the extent to which a co-culture mimics the in vivo processes. Most co-culture models depart from synovial lining and cartilage culture, but also fat pad and bone have been included. Not all of the models appear to reflect the postulated in vivo OA pathophysiology, although some of the discrepancies may indicate current assumptions on this process are not entirely valid. Systematic analysis of the mutual influence the separate compartments in a given model exert on each other and validation against in vivo or ex vivo observation is still largely lacking and would increase their added value as in vitro OA models.

Crosstalk Among circRNA/lncRNA, miRNA, and mRNA in Osteoarthritis

Osteoarthritis (OA) is a joint disease that is pervasive in life, and the incidence and mortality of OA are increasing, causing many adverse effects on people's life. Therefore, it is very vital to identify new biomarkers and therapeutic targets in the clinical diagnosis and treatment of OA. ncRNA is a nonprotein-coding RNA that does not translate into proteins but participates in protein translation. At the RNA level, it can perform biological functions. Many studies have found that miRNA, lncRNA, and circRNA are closely related to the course of OA and play important regulatory roles in transcription, post-transcription, and post-translation, which can be used as biological targets for the prevention, diagnosis, and treatment of OA. In this review, we summarized and described the various roles of different types of miRNA, lncRNA, and circRNA in OA, the roles of different lncRNA/circRNA-miRNA-mRNA axis in OA, and the possible prospects of these ncRNAs in clinical application.

Elucidating mechano-pathology of osteoarthritis: transcriptome-wide differences in mechanically stressed aged human cartilage explants

Background

Failing of intrinsic chondrocyte repair after mechanical stress is known as one of the most important initiators of osteoarthritis. Nonetheless, insight into these early mechano-pathophysiological processes in age-related human articular cartilage is still lacking. Such insights are needed to advance clinical development. To highlight important molecular processes of osteoarthritis mechano-pathology, the transcriptome-wide changes following injurious mechanical stress on human aged osteochondral explants were characterized.

Methods

Following mechanical stress at a strain of 65% (65%MS) on human osteochondral explants (n_65%MS = 14 versus n_control = 14), RNA sequencing was performed. Differential expression analysis between control and 65%MS was performed to determine mechanical stress-specific changes. Enrichment for pathways and protein-protein interactions was analyzed with Enrichr and STRING.

Results

We identified 156 genes significantly differentially expressed between control and 65%MS human osteochondral explants. Of note, IGFBP5 (FC = 6.01; FDR = 7.81 × 10⁻³) and MMP13 (FC = 5.19; FDR = 4.84 × 10⁻²) were the highest upregulated genes, while IGFBP6 (FC = 0.19; FDR = 3.07 × 10⁻⁴) was the most downregulated gene. Protein-protein interactions were significantly higher than expected by chance (P = 1.44 × 10⁻¹⁵ with connections between 116 out of 156 genes). Pathway analysis showed, among others, enrichment for cellular senescence, insulin-like growth factor (IGF) I and II binding, and focal adhesion.

Conclusions

Our results faithfully represent transcriptomic wide consequences of mechanical stress in human aged articular cartilage with MMP13, IGF binding proteins, and cellular senescence as the most notable results. Acquired knowledge on the as such identified initial, osteoarthritis-related, detrimental responses of chondrocytes may eventually contribute to the development of effective disease-modifying osteoarthritis treatments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02595-8.

α-Cyperone (CYP) down-regulates NF-κB and MAPKs signaling, attenuating inflammation and extracellular matrix degradation in chondrocytes, to ameliorate osteoarthritis in mice

Inflammation and extracellular matrix (ECM) degradation have been implicated in the pathological process of osteoarthritis (OA). α-Cyperone is the main active component of the traditional Chinese medicine Cyperus rotundus L. In this study, we found that α-Cyperone abolished the IL-1β-induced production of inflammatory cytokines in isolated rat chondrocytes, such as cyclooxygenase-2 (COX-2), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) and inducible nitric oxide synthase (iNOS), in a dose-dependent manner (0.75, 1.5 or 3 μM). Also, the results showed that α-Cyperone downregulated the expression of metalloproteinases (MMPs) and thrombospondin motifs 5 (ADAMTS5), and upregulated the expression of type-2 collagen. Mechanistically, molecular docking tests revealed that α-Cyperone stably and effectively binds to p65, p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK). α-Cyperone inhibited NF-κB activation by blocking its nuclear transfer, and decreasing the phosphorylation of mitogen-activated protein kinase (MAPKs). In addition, in vivo studies based on a mouse model of arthritis showed that α-Cyperone prevented the development of osteoarthritis. Therefore, α-Cyperone may be a potential anti-OA drug.

Nuclear Magnetic Resonance Therapy Modulates the miRNA Profile in Human Primary OA Chondrocytes and Antagonizes Inflammation in Tc28/2a Cells

Nuclear magnetic resonance therapy (NMRT) is discussed as a participant in repair processes regarding cartilage and as an influence in pain signaling. To substantiate the application of NMRT, the underlying mechanisms at the cellular level were studied. In this study microRNA (miR) was extracted from human primary healthy and osteoarthritis (OA) chondrocytes after NMR treatment and was sequenced by the Ion PI Hi-Q™ Sequencing 200 system. In addition, T/C-28a2 chondrocytes grown under hypoxic conditions were studied for IL-1β induced changes in expression on RNA and protein level. HDAC activity an NAD⁽⁺⁾/NADH was measured by luminescence detection. In OA chondrocytes miR-106a, miR-27a, miR-34b, miR-365a and miR-424 were downregulated. This downregulation was reversed by NMRT. miR-365a-5p is known to directly target HDAC and NF-ĸB, and a decrease in HDAC activity by NMRT was detected. NAD⁺/NADH was reduced by NMR treatment in OA chondrocytes. Under hypoxic conditions NMRT changed the expression profile of HIF1, HIF2, IGF2, MMP3, MMP13, and RUNX1. We conclude that NMRT changes the miR profile and modulates the HDAC and the NAD⁽⁺⁾/NADH signaling in human chondrocytes. These findings underline once more that NMRT counteracts IL-1β induced changes by reducing catabolic effects, thereby decreasing inflammatory mechanisms under OA by changing NF-ĸB signaling.

Cartilage Protective and Immunomodulatory Features of Osteoarthritis Synovial Fluid-Treated Adipose-Derived Mesenchymal Stem Cells Secreted Factors and Extracellular Vesicles-Embedded miRNAs

Intra-articular administration of adipose-derived mesenchymal stem cells (ASCs), either in vitro expanded or within adipose tissue-based products obtained at point-of-care, has gained popularity as innovative regenerative medicine approach for osteoarthritis (OA) treatment. ASCs can stimulate tissue repair and immunomodulation through paracrine factors, both soluble and extracellular vesicles (EV) embedded, collectively defining the secretome. Interaction with the degenerative/inflamed environment is a crucial factor in understanding the finely tuned molecular message but, to date, the majority of reports have described ASC-secretome features in resting conditions or under chemical stimuli far from the in vivo environment of degenerated OA joints. In this report, the secretory profile of ASCs treated with native synovial fluid from OA patients was evaluated, sifting 200 soluble factors and 754 EV-embedded miRNAs. Fifty-eight factors and 223 EV-miRNAs were identified, and discussed in the frame of cartilage and immune cell homeostasis. Bioinformatics gave a molecular basis for M2 macrophage polarization, T cell proliferation inhibition and T reg expansion enhancement, as well as cartilage protection, further confirmed in an in vitro model of OA chondrocytes. Moreover, a strong influence on immune cell chemotaxis emerged. In conclusion, obtained molecular data support the regenerative and immunomodulatory properties of ASCs when interacting with osteoarthritic joint environment.

Anti-Inflammatory Effects of Conditioned Medium of Periodontal Ligament-Derived Stem Cells on Chondrocytes, Synoviocytes, and Meniscus Cells

Osteoarthritis (OA) is the most common type of arthritis, afflicting millions of people in the world. Elevation of inflammatory mediators and enzymatic matrix destruction is often associated with OA. Therefore, the objective of this study was to investigate the effects of conditioned medium from periodontal ligament-derived stem cells (PDLSCs) on inflammatory and catabolic gene expressions of chondrocytes, synoviocytes, and meniscus cells under in vitro inflammatory condition. Stem cells were isolated from human periodontal ligaments. Conditioned medium was collected and concentrated 20 × . Chondrocytes, synoviocytes, and meniscus cells were isolated from pig knees and divided into four experimental groups: serum-free media, serum-free media+interleukin-1β (IL-1β) (10 ng/mL), conditioned media (CM), and CM+IL-1β. Protein content and extracellular vesicle (EV) miRNAs of CM were analyzed by liquid chromatography-tandem mass spectrometry and RNA sequencing, respectively. It was found that the IL-1β treatment upregulated the expression of IL-1β, tumor necrosis factor-α (TNF-α), MMP-13, and ADAMTS-4 genes in the three cell types, whereas PDLSC-conditioned medium prevented the upregulation of gene expression by IL-1β in all three cell types. This study also found that there was consistency in anti-inflammatory effects of PDLSC CM across donors and cell subcultures, while PDLSCs released several anti-inflammatory factors and EV miRNAs at high levels. OA has been suggested as an inflammatory disease in which all intrasynovial tissues are involved. PDLSC-conditioned medium is a cocktail of trophic factors and EV miRNAs that could mediate different inflammatory processes in various tissues in the joint. Introducing PDLSC-conditioned medium to osteoarthritic joints could be a potential treatment to prevent OA progression by inhibiting inflammation.

Myc is involved in Genistein protecting against LPS-induced myocarditis in vitro through mediating MAPK/JNK signaling pathway

BACKGROUND

Genistein is widely used as a pharmacological compound as well as a food additive. However, the pharmaceutical effects of Genistein on myocarditis and its potential mechanisms have not been studied in detail.

METHODS

H9c2 cells were continuously stimulated by lipopolysaccharide (LPS) for 12 h to simulate the in vitro model of myocarditis injury. DrugBank, String, and GEO dataset were used to investigate specific genes that interacting with Genistein. KEGG and GO enrichment analysis were employed to explore Myc-related signaling pathways. Biological behaviors of H9c2 cells were observed with the support of cell counting kit-8, MTT and flow cytometry. Expression levels of cytokines including TNF-α and ILs were evaluated by enzyme-linked immunosorbent assay. Western blot was applied to detect the expression of Myc and MAPK pathway related proteins.

RESULTS

Genistein alleviated the damage of H9c2 cells subjected to LPS from the perspective of elevating cells growth ability, and inhibiting cells apoptosis and inflammatory response. Through bioinformatics analysis, we identified Myc as the potential target of Genistein in myocarditis, and MAPK as the signaling pathway. Significantly, Myc was highly up-regulated in myocarditis samples. More importantly, by performing biological experiments, we discovered that Genistein relieved H9c2 cells apoptosis and inflammatory reaction which caused by LPS stimulation through inhibiting Myc expression. Additionally, the marked augmentation of p-P38 MAPK and p-JNK expression in LPS-induced cardiomyocyte model were blocked by Genistein and si-Myc.

CONCLUSIONS

Our research revealed that Myc mediated the protective effects of Genistein on H9c2 cells damage caused by LPS partly through modulation of MAPK/JNK signaling pathway.

Amniotic membrane-mesenchymal stromal cells secreted factors and extracellular vesicle-miRNAs: Anti-inflammatory and regenerative features for musculoskeletal tissues

Human amniotic membrane‐derived mesenchymal stromal cells (hAMSCs) are easily obtained in large quantities and free from ethical concerns. Promising therapeutic results for both hAMSCs and their secreted factors (secretome) were described by several in vitro and preclinical studies, often for treatment of orthopedic disorders such as osteoarthritis (OA) and tendinopathy. For clinical translation of the hAMSC secretome as cell‐free therapy, a detailed characterization of hAMSC‐secreted factors is mandatory. Herein, we tested the presence of 200 secreted factors and 754 miRNAs in extracellular vesicles (EVs). Thirty‐seven cytokines/chemokines were identified at varying abundance, some of which involved in both chemotaxis and homeostasis of inflammatory cells and in positive remodeling of extracellular matrix, often damaged in tendinopathy and OA. We also found 336 EV‐miRNAs, 51 of which accounted for more than 95% of the genetic message. A focused analysis based on miRNAs related to OA and tendinopathy showed that most abundant EV‐miRNAs are teno‐ and chondro‐protective, able to induce M2 macrophage polarization, inhibit inflammatory T cells, and promote Treg. Functional analysis on IL‐1β treated tenocytes and chondrocytes resulted in downregulation of inflammation‐associated genes. Overall, presence of key regulatory molecules and miRNAs explain the promising therapeutic results of hAMSCs and their secretome for treatment of musculoskeletal conditions and are a groundwork for similar studies in other pathologies. Furthermore, identified molecules will pave the way for future studies aimed at more sharply predicting disease‐targeted clinical efficacy, as well as setting up potency and release assays to fingerprint clinical‐grade batches of whole secretome or purified components.

Identification of Diagnostic Biomarkers of Osteoarthritis Based on Multi-Chip Integrated Analysis and Machine Learning

The pathogenesis of osteoarthritis (OA) is still unclear. It is therefore important to identify relevant diagnostic marker genes for OA. We performed an integrated analysis with multiple microarray data cohorts to identify potential transcriptome markers of OA development. Further, to identify OA diagnostic markers, we established gene regulatory networks based on the protein-protein interaction network involved in these differentially expressed genes (DEGs). Using support vector machine (SVM) pattern recognition, a diagnostic model for OA prediction and prevention was established. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed that 190 DEGs were mainly enriched in pathways like the tumor necrosis factor signaling pathway, interleukin-17 signaling pathway, mitogen-activated protein kinase signaling pathway, nuclear factor kappa-light-chain-enhancer of activated B cells signaling pathway, and osteoclast differentiation. Eight hub genes (POSTN, MMP2, CTSG, ELANE, COL3A1, MPO, COL1A1, and COL1A2) were considered potential diagnostic biomarkers for OA, the area under curve (AUC) was >0.95, which showed high accuracy. The sensitivity and specificity of the SVM model of OA based on these eight genes reached 100% in multiple external verification cohorts. Our research provides a theoretical basis for OA diagnosis for clinicians.

Hypoxia Induces Mitochondrial Defect That Promotes T Cell Exhaustion in Tumor Microenvironment Through MYC-Regulated Pathways

T cell exhaustion is an obstacle to immunotherapy for solid tumors. An understanding of the mechanism by which T cells develop this phenotype in solid tumors is needed. Here, hypoxia, a feature of the tumor microenvironment, causes T cell exhaustion (T_Exh) by inducing a mitochondrial defect. Upon exposure to hypoxia, activated T cells with a T_Exh phenotype are characterized by mitochondrial fragmentation, decreased ATP production, and decreased mitochondrial oxidative phosphorylation activity. The T_Exh phenotype is correlated with the downregulation of the mitochondrial fusion protein mitofusin 1 (MFN1) and upregulation of miR-24. Overexpression of miR-24 alters the transcription of many metabolism-related genes including its target genes MYC and fibroblast growth factor 11 (FGF11). Downregulation of MYC and FGF11 induces T_Exh differentiation, reduced ATP production and a loss of the mitochondrial mass in T cell receptor (TCR)-stimulated T cells. In addition, we determined that MYC regulates the transcription of FGF11 and MFN1. In nasopharyngeal carcinoma (NPC) tissues, the T cells exhibit an increased frequency of exhaustion and loss of mitochondrial mass. In addition, inhibition of miR-24 signaling decreases NPC xenograft growth in nude mice. Our findings reveal a mechanism for T cell exhaustion in the tumor environment and provide potential strategies that target mitochondrial metabolism for cancer immunotherapy.

How microRNAs affect the PD-L1 and its synthetic pathway in cancer

Programmed cell death-ligand 1 (PD-L1) is a glycoprotein that is expressed on the cell surface of both hematopoietic and nonhematopoietic cells. PD-L1 play a role in the immune tolerance and protect self-tissues from immune system attack. Dysfunction of this molecule has been highlighted in the pathogenesis of tumors, autoimmunity, and infectious disorders. MicroRNAs (miRNAs) are endogenous molecules that are classified as small non-coding RNA with approximately 20-22 nucleotides (nt) length. The function of miRNAs is based on complementary interactions with target mRNA via matching completely or incompletely. The result of this function is decay of the target mRNA or preventing mRNA translation. In the past decades, several miRNAs have been discovered which play an important role in the regulation of PD-L1 in various malignancies. In this review, we discuss the effect of miRNAs on PD-L1 expression and consider the effect of miRNAs on the synthetic pathway of PD-L1, especially during cancers.

Secreted Factors and EV-miRNAs Orchestrate the Healing Capacity of Adipose Mesenchymal Stem Cells for the Treatment of Knee Osteoarthritis

Mesenchymal stem cells (MSCs) derived from adipose tissue and used either as expanded cells or minimally manipulated cell preparations showed positive clinical outcomes in regenerative medicine approaches based on tissue restoration and inflammation control, like in osteoarthritis (OA). Recently, MSCs’ healing capacity has been ascribed to the large array of soluble factors, including soluble cytokines/chemokines and miRNAs conveyed within extracellular vesicles (EVs). Therefore, in this study, 200 secreted cytokines, chemokines and growth factors via ELISA, together with EV-embedded miRNAs via high-throughput techniques, were scored in adipose-derived MSCs (ASCs) cultivated under inflammatory conditions, mimicking OA synovial fluid. Both factors (through most abundantly expressed TIMP1, TIMP2, PLG and CTSS) and miRNAs (miR-24-3p, miR-222-3p and miR-193b-3p) suggested a strong capacity for ASCs to reduce matrix degradation activities, as those activated in OA cartilage, and switch synovial macrophages, often characterized by an M1 inflammatory polarization, towards an M2 phenotype. Moreover, the crucial importance of selecting the target tissue is discussed, showing how a focused search may greatly improve potency prediction and explain clinical outcomes. In conclusion, herein presented data shed light about the way ASCs regulate cell homeostasis and regenerative pathways in an OA-resembling environment, therefore suggesting a rationale for the use of MSC-enriched clinical products, such as stromal vascular fraction and microfragmented adipose tissue, in joint pathologies.

DNA methylation is involved in the pathogenesis of osteoarthritis by regulating CtBP expression and CtBP-mediated signaling

Osteoarthritis (OA) is a common type of arthritis. Chronic inflammation is an important contributor to the pathogenesis of OA. The maturation and secretion of proinflammatory cytokines are controlled by inflammasomes, especially NLRP1 (NLR Family Pyrin Domain Containing 1) and NLRP3. In this study, we identified a transactivation mechanism of NLRP3 mediated by CtBPs (C-terminal-binding proteins). We found that both the mRNA and protein levels of CtBPs were significantly increased in OA biopsies. Analyzing the profiles of differentially expressed genes in CtBP-knockdown and overexpression cells, we found that the expression of NLRP3 was dependent on CtBP levels. By the knockdown or overexpression of transcription factors that potentially bind to the promoter of NLRP3, we found that only AP1 could specifically regulate the expression of NLRP3. Using immunoprecipitation (IP) and Co-IP assays, we found that AP1 formed a transcriptional complex with a histone acetyltransferase p300 and CtBPs. The knockdown of any member of this transcriptional complex resulted in a decrease in the expression of NLRP3. To explore the underlying mechanism of CtBP overexpression, we analyzed their promoters and found that they were abundant in CpG islands. Treatment with the DNA methylation inhibitor 5-aza-2′-deoxycytidine (AZA) or knockdown of DNMTs (DNA methyltransferases) resulted in the overexpression of CtBPs, while overexpression of DNMTs caused the reverse effects on CtBP expression. Collectively, our results suggest that the decreased DNA methylation levels in the promoters of CtBPs upregulate their expression. Increased CtBPs associated with p300 and AP1 to form a transcriptional complex and activate the expression of NLRP3 and its downstream signaling, eventually aggravating the inflammatory response and leading to the pathogenesis of OA.

Noncoding RNAs: New regulatory code in chondrocyte apoptosis and autophagy

Osteoarthritis (OA) is a bone and joint disease characterized by progressive cartilage degradation. In the face of global trends of population aging, OA is expected to become the fourth most common disabling disease by 2020. Nevertheless, the detailed pathogenesis of OA has not yet been elucidated. Noncoding RNAs (ncRNAs), including long noncoding RNAs, microRNAs, and circular RNAs, do not encode proteins but have recently emerged as important regulators of apoptosis and autophagy of chondrocytes, thereby highlighting a potential role in chondrocyte injury leading to OA onset and progression. We here review recent findings on these regulatory roles of ncRNAs to provide new directions for research on the pathogenesis of OA and offer new therapeutic targets for prevention and treatment. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA in Disease and Development > RNA in Development.

Kartogenin enhances the therapeutic effect of bone marrow mesenchymal stem cells derived exosomes in cartilage repair

The effectiveness of mesenchymal stem cells (MSC) in the treatment of cartilage diseases has been demonstrated to be attributed to the paracrine mechanisms, especially the mediation of exosomes. But the exosomes derived from unsynchronized MSCs may be nonhomogeneous and the therapeutic effect varies between samples. Aim: To produce homogeneous and more effective exosomes for the regeneration of cartilage. Materials & methods: In this study we produced specific exosomes from bone marrow MSCs (BMSC) through kartogenin (KGN) preconditioning and investigated their performance in either in vitro or in vivo experiments. Results & conclusion: The exosomes derived from KGN-preconditioned BMSCs (KGN-BMSC-Exos) performed more effectively than the exosomes derived from BMSCs (BMSC-Exos). KGN preconditioning endowed BMSC-Exos with stronger chondral matrix formation and less degradation.

Non-Coding RNAs in Cartilage Development: An Updated Review

In the development of the skeleton, the long bones are arising from the process of endochondral ossification (EO) in which cartilage is replaced by bone. This complex process is regulated by various factors including genetic, epigenetic, and environmental elements. It is recognized that DNA methylation, higher-order chromatin structure, and post-translational modifications of histones regulate the EO. With emerging understanding, non-coding RNAs (ncRNAs) have been identified as another mode of EO regulation, which is consist of microRNAs (miRNAs or miRs) and long non-coding RNAs (lncRNAs). There is expanding experimental evidence to unlock the role of ncRNAs in the differentiation of cartilage cells, as well as the pathogenesis of several skeletal disorders including osteoarthritis. Cutting-edge technologies such as epigenome-wide association studies have been employed to reveal disease-specific patterns regarding ncRNAs. This opens a new avenue of our understanding of skeletal cell biology, and may also identify potential epigenetic-based biomarkers. In this review, we provide an updated overview of recent advances in the role of ncRNAs especially focus on miRNA and lncRNA in the development of bone from cartilage, as well as their roles in skeletal pathophysiology.

Identification of key gene modules and transcription factors for human osteoarthritis by weighted gene co-expression network analysis

Osteoarthritis (OA) is one of the most prevalent causes of joint disease. However, the pathological mechanisms of OA have remained to be completely elucidated, and further investigation into the underlying mechanisms of OA development and the identification of novel therapeutic targets are urgently required. In the present study, the dataset GSE114007 was downloaded from the Gene Expression Omnibus database. Based on weighted gene co-expression network analysis (WGCNA) and the identification of differentially expressed genes (DEGs), the microarray data were further analyzed to identify hub genes, key transcription factors (TFs) and pivotal signaling pathways involved in the pathogenesis of OA. A total of 1,898 genes were identified to be differentially expressed between OA samples and normal samples. Based on WGCNA, the present study identified 5 hub modules closely associated with OA, and the potential key TFs for hub modules were further explored based on CisTargetX. The results demonstrated that B-Cell Lymphoma 6, Myelin Gene Expression Factor 2, Activating Transcription Factor 3, CCAAT Enhancer Binding Protein γ, Nuclear Factor Interleukin-3-Regulated, FOS Like Antigen-2, FOS-Like Antigen-1, Fos Proto-Oncogene, JunD Proto-Oncogene, Transcription Factor CP2 Like 1, RELA proto-oncogene NF-kB subunit, SRY-box transcription factor 3, V-Ets Avian Erythroblastosis Virus E26 Oncogene Homolog 2, Interferon Regulatory Factor 4 and REL proto-oncogene, NF-kB subunit were the potential key TFs. In addition, osteoclast differentiation, FoxO, MAPK and PI3K/Akt signaling pathways were revealed to be imperative for the pathogenesis of OA, as these 4 pivotal signaling pathways were observed to be tightly linked through 4 key TFs Fos Proto-Oncogene, JUN, JunD Proto-Oncogene and MYC, and 4 DEGs Vascular Endothelial Growth Factor A, Growth Arrest and DNA Damage Inducible α, Growth Arrest and DNA Damage Inducible β and Cyclin D1. The present study identified a set of potential key genes and signaling pathways, and provided an important opportunity to advance the current understanding of OA.

RETRACTED: ANRIL acts as onco-lncRNA by regulation of microRNA-24/c-Myc, MEK/ERK and Wnt/β-catenin pathway in retinoblastoma

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Authors. Current research findings in the authors' laboratory are in conflict with previous experimental results published in this paper. It was found that the data reported in figures 4 and 5 were not able to be replicated and so therefore the authors have decided that it is best for the scientific record to retract this paper. All the authors agree with the retraction. The authors apologise for any confusion this paper might have caused readers.

Paradoxical effects of cellular senescence-inhibited gene involved in hepatocellular carcinoma migration and proliferation by ERK pathway and mesenchymal-like markers

BACKGROUND

Cellular senescence-inhibited gene (CSIG) strongly prolongs the progression of replicative senescence. However, roles and mechanisms of CSIG in tumor progression have not been studied widely.

METHODS

Roles of CSIG in migration and proliferation of SMMC7721 and Huh7 cells were analyzed by transwell or cell viability assays, respectively. Tumorigenicity assays were used to study whether CSIG knockdown could affect SMMC7721 proliferation in vivo. Next, Western blotting and RT-PCR were preformed to evaluate the effects of CSIG on P-ERK cascade and epithelial mesenchymal transformation markers. Then, the location and expression of CSIG protein was detected by immunofluorescence and Western blotting, respectively. Finally, the Cancer Genome Atlas dataset was used to analyze CSIG mRNA levels in hepatocellular carcinoma (HCC) and adjacent non-tumor tissues.

RESULTS

In this study, we found that CSIG overexpression promoted SMMC7721 cell migration, and CSIG knockdown suppressed tumorigenicity of SMMC7721 cells. In contrast to expectation, CSIG up-regulation could significantly inhibit Huh7 cell growth and migration. CSIG could promote P-ERK activation and levels of mesenchymal-like markers in SMMC7721 cells, whereas CSIG suppressed P-ERK activation and levels of mesenchymal-like markers in Huh7 cells. CSIG protein was located in nucleoli as well as nucleoplasm of SMMC7721 cells, whereas CSIG protein was mainly expressed in the nucleoli rather than nucleoplasm of Huh7 cells. Finally, due to individual differences, raised or down-regulated trends of CSIG in HCC as compared with adjacent non-tumor tissues are different among various patient populations.

CONCLUSION

In summary, these results indicate that CSIG might play different roles in SMMC7721 and Huh7 cells through regulating P-ERK pathway and mesenchymal-like markers. The differential distribution of CSIG might be an important factor that causes its different functions in SMMC7721 and Huh7 cells. CSIG might play different roles in various patient populations.

Ligustilide attenuates nitric oxide-induced apoptosis in rat chondrocytes and cartilage degradation via inhibiting JNK and p38 MAPK pathways

Ligustilide (LIG) is the main lipophilic component of the Umbelliferae family of pharmaceutical plants, including Radix angelicae sinensis and Ligusticum chuanxiong. LIG shows various pharmacological properties associated with anti‐inflammation and anti‐apoptosis in several kinds of cell lines. However, the therapeutic effects of LIG on chondrocyte apoptosis remain unknown. In this study, we investigated whether LIG had an anti‐apoptotic activity in sodium nitroprusside (SNP)‐stimulated chondrocyte apoptosis and could delay cartilage degeneration in a surgically induced rat OA model, and elucidated the potential mechanisms. In vitro studies revealed that LIG significantly suppressed chondrocyte apoptosis and cytoskeletal remodelling, which maintained the nuclear morphology and increased the mitochondrial membrane potential. In terms of SNP, LIG treatment considerably reduced the expression levels of cleaved caspase‐3, Bax and inducible nitric oxide synthase and increased the expression level of Bcl‐2 in a dose‐dependent manner. The LIG‐treated groups presented a significantly suppressed expression of activating transcription factor 2 and phosphorylation of Jun N‐terminal kinase (JNK) and p38 mitogen‐activated protein kinase (MAPK). The inhibitory effect of LIG was enhanced by the p38 MAPK inhibitor SB203580 or the JNK inhibitor SP600125 and offset by the agonist anisomycin. In vivo studies demonstrated that LIG attenuated osteoarthritic cartilage destruction by inhibiting the cartilage chondrocyte apoptosis and suppressing the phosphorylation levels of activating transcription factor 2, JNK and p38 MAPK. This result was confirmed by histological analyses, micro‐CT, TUNEL assay and immunohistochemical analyses. Collectively, our studies indicated that LIG protected chondrocytes against SNP‐induced apoptosis and delayed articular cartilage degeneration by suppressing JNK and p38 MAPK pathways.

MiR-15b is a key regulator of proliferation and apoptosis of chondrocytes from patients with condylar hyperplasia by targeting IGF1, IGF1R and BCL2

OBJECTIVE

This study aimed to explore potential microRNAs (miRNAs), which participate in the pathological process of condylar hyperplasia (CH) through targeting specific proliferation- and apoptosis- related genes of chondrocytes.

METHODS

Insulin-like growth factor 1 (IGF1), IGF1 receptor (IGF1R) and B-cell CLL/lymphoma 2 (BCL2) in CH cartilage were detected by real-time polymerase chain reaction (PCR), Western blot, immunohistochemistry and immunofluorescence. MiRanda and TargetScanS algorithms were used to predict certain miRNAs in CH chondrocytes concurrently modulating the above three genes. MiR-15b was screened and identified using real-time PCR. After transfection of miR-15b mimics or inhibitor into CH chondrocytes, expression of the above three genes was detected by real-time PCR and western blot, meanwhile, cell proliferation and apoptosis was examined by CCK8, cell cycle assays, flow cytometry and Hoechst staining. Dual luciferase activity was performed to identify the direct regulation of miR-15b on IGF1, IGF1R and BCL2.

RESULTS

Expression of IGF1, IGF1R and BCL2 increased in CH cartilage. Seven microRNAs concurrently correlated with IGF1, IGF1R and BCL2. Among them, only miR-15b significantly changed in CH chondrocytes. Overexpression of miR-15b in CH chondrocytes suppressed the expression of IGF1, IGF1R and BCL2, while it increased when miR-15b was knockdown. Furthermore, miR-15b suppressed their expression by directly binding to its 3'-UTR in these cells. Besides, miR-15b hampered chondrocytes proliferation through targeting IGF1 and IGF1R and accelerated chondrocytes apoptosis through targeting BCL2.

CONCLUSION

Suppressed miR-15b contributed to enhanced proliferation capacity and weakened apoptosis of chondrocytes through augmentation of IGF1, IGF1R and BCL2, thereby resulting in development of CH.

MicroRNA‑93 inhibits chondrocyte apoptosis and inflammation in osteoarthritis by targeting the TLR4/NF‑κB signaling pathway

Osteoarthritis (OA) is a serious disease of the articular cartilage, and inflammation has been implicated in its pathogenesis. Previously, microRNAs (miRNAs) have been proposed as novel regulators of inflammation, however, the functional role of microRNAs in regulating inflammation in OA remains to be fully elucidated. The aim of the present study was to investigate the roles of miRNAs in OA inflammation and the underlying molecular mechanism. Firstly, the miRNA expression patterns were analyzed in the articular cartilage tissues from experimental OA mice using an miRNA microarray. miRNA (miR)-93 was identified with particular interest due to its reported effects on apoptosis and inflammation suppression. Subsequently, the expression of miR-93 was further validated in the articular cartilage tissues of OA mice and lipopolysaccharide (LPS)-stimulated primary chondrocytes. Using this LPS-induced chondrocyte injury model, the overexpression of miR-93 enhanced cell viability, improved cell apoptosis and attenuated the inflammatory response, as reflected by reductions in pro-inflammatory cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6. In addition, Toll-like receptor 4 (TLR4), an important regulator of the nuclear factor-κB (NF-κB) signaling pathway, was identified as a direct target of miR-93 in chondrocytes. Furthermore, the restoration of TLR4 markedly abrogated the inhibitory effects of miR-93 on the chondrocyte apoptosis and inflammation induced by LPS. In addition, the overexpression of miR-93 by agomir-miR-93 significantly inhibited the levels of pro-inflammatory cytokines and cell apoptosis, whereas antagomir-93 exacerbated apoptosis and inflammation in vivo. Taken together, the results of the study suggested that miR-93 may be a promising therapeutic target for the treatment of human OA.

Interleukin‑10 promotes proliferation and migration, and inhibits tendon differentiation via the JAK/Stat3 pathway in tendon‑derived stem cells in vitro

Tendon repair follows a slow course of early inflammatory, proliferative and remodeling phases, which commonly results in the failure and loss of normal biomechanical properties. Previous studies have demonstrated that tendon-derived stem cells (TDSCs) are vital healing cells and that mRNA expression of anti-inflammatory cytokine interleukin (IL)-10 is significantly upregulated at the late inflammatory phase. To explore how IL-10 may impact tendon healing, the present study investigated the in vitro effects of IL-10 on TDSCs isolated from rat Achilles tendons. Cellular activities of TDSCs and the expression levels of tendon cell markers were measured treatment with IL-10 and subsequent performance of wound healing assays, reverse transcription-quantitative polymerase chain reaction and western blot analyses. The results demonstrated that IL-10 treatment markedly increased the proliferative capacity of TDSCs. In addition, IL-10 significantly enhanced cell migration when compared with the control cells. Furthermore, IL-10 treatment significantly activated the JAK/Stat3 signaling pathway and inhibited the protein expression of tendon cell markers, including scleraxis and tenomodulin. Notably, IL-10 treatment also reduced the gene expression levels of type 1 collagen, type 3 collagen, lumican and fibromodulin in TDSCs. These findings indicated that IL-10 enhanced cell proliferation and migration, and inhibited tenogenic differentiation in TDSCs in vitro. Reducing the negative effects whilst enhancing the positive effects of IL-10 may be a potential therapeutic target in tendon repair.

The complex landscape of microRNAs in articular cartilage: biology, pathology, and therapeutic targets

The disabling degenerative disease osteoarthritis (OA) is prevalent among the global population. Articular cartilage degeneration is a central feature of OA; therefore, a better understanding of the mechanisms that maintain cartilage homeostasis is vital for developing effective therapeutic interventions. MicroRNAs (miRs) modulate cell signaling pathways and various processes in articular cartilage via posttranscriptional repression of target genes. As dysregulated miRs frequently alter the homeostasis of articular cartilage, modulating select miRs presents a potential therapeutic opportunity for OA. Here, we review key miRs that have been shown to modulate cartilage-protective or -destructive mechanisms and signaling pathways. Additionally, we use an integrative computational biology approach to provide insight into predicted miR gene targets that may contribute to OA pathogenesis, and highlight the complexity of miR signaling in OA by generating both unique and overlapping gene targets of miRs that mediate protective or destructive effects. Early OA detection would enable effective prevention; thus, miRs are being explored as diagnostic biomarkers. We discuss these ongoing efforts and the applicability of miR mimics and antisense inhibitors as potential OA therapeutics.

Integration of Gene Expression Profile Data to Screen and Verify Hub Genes Involved in Osteoarthritis

Osteoarthritis (OA) is one of the most common diseases worldwide, but the pathogenic genes and pathways are largely unclear. The aim of this study was to screen and verify hub genes involved in OA and explore potential molecular mechanisms. The expression profiles of GSE12021 and GSE55235 were downloaded from the Gene Expression Omnibus (GEO) database, which contained 39 samples, including 20 osteoarthritis synovial membranes and 19 matched normal synovial membranes. The raw data were integrated to obtain differentially expressed genes (DEGs) and were deeply analyzed by bioinformatics methods. The Gene Ontology (GO) and pathway enrichment of DEGs were performed by DAVID and Kyoto Encyclopedia of Genes and Genomes (KEGG) online analyses, respectively. The protein-protein interaction (PPI) networks of the DEGs were constructed based on data from the STRING database. The top 10 hub genes VEGFA, IL6, JUN, IL1β, MYC, IL4, PTGS2, ATF3, EGR1, and DUSP1 were identified from the PPI network. Module analysis revealed that OA was associated with significant pathways including TNF signaling pathway, cytokine-cytokine receptor interaction, and osteoclast differentiation. The qRT-PCR result showed that the expression level of IL6, VEGFA, JUN, IL-1β, and ATF3 was significantly increased in OA samples (p < 0.05), and these candidate genes could be used as potential diagnostic biomarkers and therapeutic targets of OA.

Hydroxysafflor yellow A (HSYA) targets the NF-κB and MAPK pathways and ameliorates the development of osteoarthritis

The inflammatory environment has been demonstrated to be strongly associated with the progression of osteoarthritis (OA).

Retracted Article: PVT1 depletion protects cartilage ATDC5 cells against LPS-induced inflammatory injury by regulating the miR-24/ADAMTS5 axis

Osteoarthritis is a common chronic arthritis among adults and cartilage dysfunction is largely responsible for osteoarthritis development.